/Engine/Source/Runtime/SlateCore/Public/Brushes/SlateNoResource.h
This represents an undefined brush.FSlateNoResourceis a valid brush which means don't render anything.FSlateOptionalBrushmeans let the widget decide what to do if the brush is unset. Widgets that don't check for the brush being unspecified will draw nothing
struct FSlateOptionalBrush : public [FSlateBrush](API\Runtime\SlateCore\Styling\FSlateBrush)